Our aim is to study specific malarial parasite proteins that alter the surface of the host red cell, and in so doing play an essential role in the parasite's ability to survive. Understanding the action of these parasite proteins may lead to novel methods of inhibiting growth of parasites in man. Studies are planned which will extend our preliminary results suggesting that iron transport activity absent in normal mature red cells appears once they are invaded by Plasmsdia. l. We want to study the mechanisms of iron transport in P. falciparum-infected red cells by measuring the binding of radiolabelled transferrin to a receptor, possibly of parasite origin, which is present in the red cell membrane. We will then use antibodies to transferrin to isolate the transferrin-receptor complex from the membranes of infected cells. l25I labelled transferrin will also be used to probe "Western" gel blots of SDS-PAGE resolved parasite proteins. 2. The route of uptake and subcellular location of the transferrin-receptor complex in parasitized erythrocytes will be investigated using different electron microscopic techniques including incubation and transferrin coupled to electron-dense markers and immunolabeling of ultra-thin sections with antibody to both transferrin and transferrin receptor. 3. We will determine whether the parasite carries in its DNA the information to code for iron transport and iron storage proteins by screening genomic DNA of both P. chabaudi and P. falciparum with cDNA probes for human transferrin receptor and for ferritin, and by screening lambda cDNA libraries of P. chabaudi with these probes as well as with antibodies. We will also test whether there is temporal regulation of these genes by following the accumulation of mRNA for these proteins in the different developmental stages of the parasite. Differences between the human and P. falciparum sequences might be used to localize immunogenic peptides within the parasite receptor. Presumably such regions are hidden from the host immune system in vivo. However, synthetic peptides constructed to emulate these regions may be useful as protective antigens.